As is well known, zipwire trolleys are used to transport people along a cable (or zipwire) fixed at one, higher, end to a suitable anchor point and fixed at another, lower, end to another anchor point which usually includes some kind of buffer arrangement, such as a shock absorber or grab rope, for slowing down the trolley at the end of the descent, which descent may at times reach speeds in excess of 150 Km/h. In order to lessen the speed of the trolley before it reaches the buffer point the zipwire is not stretched perfectly taught but is instead provided with a dip in the middle section such that as the trolley passes the lowermost point of the cable it then has to rise in order to reach the buffer point and, in so doing, slows down to a manageable level as it reaches it. However, for a variety of reasons, including the size and weight of the user of the trolley and prevailing weather conditions, it is possible that the trolley does not reach the buffer point, in which case it rolls back to the middle lowermost point of the zipwire, thereby requiring the user of the trolley to be rescued. This is both alarming and potentially hazardous for the user of the trolley, and also prevents other potential users of the zipwire from using it until the rescue has been completed, perhaps 30 minutes later.
The present invention is derived from the realisation that there is a need for a simple brake mechanism that prevents or inhibits the aforesaid problem without considerably increasing the cost or complexity of the trolley.